What does it mean if a water pump has a max head of 4 feet?
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What does it mean if a water pump has a max head of 4 feet?
That's the max height the pump will lift water. At max head, flow is greatly reduced, almost nonexistent. Manufacturers publish charts or graphs to help us select pumps, like this-
http://www.mopsdirect.us/skus/wp/Danner_Flow_Chart.asp
What do you want to do with the pump?
This should help:
total height that the pump will need to pump vertically. You will want to choose a pump that has a max head higher than the height you need to pump.
http://www.graystonecreations.com/riotable.htm
http://www.buywholesalepumps.com/riotable.htm
You also want to consider that the flow will be reduced for any vertical lift. So even if it has a max head height of 1000 ft @ 5000 GPH, it's not going to pump 5000 GPH at 500 ft, but less. This is somewhat dependent on how the lift is conducted... such as, 90 degree angles reduce it more than a slant and the more angles you have the lower the flow rate.
I don't think that's a very good way to express the idea of loss of capacity because of restriction inherent in piping or bends.Quote:
Originally Posted by ericatdallas
Certain things are always true wrt centrifugal pumps- pumps simply will not deliver to heights above their rated head, and delivery falls off rapidly as max head is approached. Small tubing and tight bends just add insult to injury wrt delivery rate.
That's why charts are important in pump selection. A safe bet is to pick a pump that will deliver the desired flow at a given height with a fair amount of headroom between that and maximum head. Reference the chart I linked above. Let's say I want 300gph at 8' of head. A model 7 would theoretically suffice, but I haven't accounted for any bends in the piping, and delivery from a model 7 falls off fast above 8' of head. If I move up to a model 9, it'll theoretically deliver more than I want, compensating for piping length & bends. I can't make a model 7 pump more than it's rated to do, but I can throttle a model 9 with a valve to deliver less if I want it to... matching pipe diameter to pump outlet diameter and using sweep bends helps keep delivery rates high. In rigid pvc, sweep bends are available in the electrical section of home centers- they're just grey instead of white.
There are more mathematical & scientific ways to size a pump to an application when the application is more complex than what we generally do for aquaria, but we really don't need to go there in general.
Never claimed to be Shakespeare :)Quote:
Originally Posted by Jhhnn
...but what I said wasn't false and it got the point I wanted to say across.
You're right, of course. No offense intended- I apologize if any was taken. I'm not Shakespeare, either.Quote:
Originally Posted by ericatdallas
Check out Ryan's post - this really explains it :
http://forum.simplydiscus.com/showth...ction&p=658411
:-)Quote:
Originally Posted by aalbina
I dealt with Ryan (Dkarc@aol.com) and he took great care of me. Just told him the length and height I was going, we talked a bit about how fast I wanted to fill and he hooked my right up.
nice tutorial, thanks!